This invention relates to blocks used for constructing a breakwater or a quay, which can effectively decrease the force of high magnitude waves while maintaining the stability of the structure thereof.
In recent years, breakwaters and quays of a type which can dissipate the energy of incident waves, thus absorbing the reflected waves and decreasing the force of the waves, have been developed.
Such a breakwater and quay are shown in FIGS. 1(a) and (b), respectively, wherein each structure substantially comprises a perforated front wall 1, an unperforated rear wall 2, and a water receiving chamber (3) defined between the front and rear walls. With such a construction, the quay can dissipate the force of the waves in the following manner. Namely, when the tops of the incident waves reach the front wall 1, the water level of the incident waves at the front wall rises resulting in a sharp difference between the water level of the incident wave and the water level of the water in the water receiving chamber 3. This phenomenon subsequently results in a rushed flow of incident wave into the water receiving chamber 3 through horizontal holes 4 formed on the apertured front wall 1. Such rushed flow causes vortices in the water receiving chamber 3, thereby efficiently decreasing the wave force. Thus, the resulting swirling stream causes an energy loss of wave energy.
After a half period of wave cycle, when the water level in the water receiving chamber rises, the bottom of the wave reaches the front wall. The water rushes out through the horizontal holes 4 from the chamber 3. Such rushed flow also causes vortices and thereby the wave force is further weakened. This implies that the reflected wave is effectively absorbed by the structure maintaining the water in the harbor as calm as possible.
In a breakwater, the incident wave hits the perforated front wall 1 first. A portion of the water then imparts a primary pressure against the front wall, while the remaining water rushes into the water receiving chamber 3. Furthermore, the portion of the remainder hits the rear wall 2, imparting a secondary pressure to the wall 2. Since a mass of the incident waves hits both front and rear walls in sequence with a time lag, the impact pressure of the wave which conventional apertured breakwaters suffer can be prevented.
To install such a quay or breakwater, large-sized caissons provided with openings have been proposed and developed. However, these caissons have the following problems in view of their construction and installation and therefore few of them have been installed commercially up to this date.
(a) Since such a caisson has holes, the carrier cannot tow the caisson from the manufacturing site to the installation site. Accordingly, the installation operation requires a large-sized carrier vessel equipped with a gigantic crane, which results in expensive installation. Such a disadvantage is especially remarkable in a small-scale installation. PA1 (b) Since the caisson which has openings cannot accommodate the packing or charging material, such a caisson is light in weight although the volume thereof is large. Therefore, this caisson lacks resistance against outer forces such as waves or earth pressures. PA1 (c) Standardization of the caissons corresponding to the size of the installation operation is impossible. PA1 (d) Since the caisson is in general large-sized, the manufacturing facilities also must be large in scale.
The operation of such facilities is costly.
Accordingly, in recent times, a method to construct breakwaters with blocks has been proposed.
In installing such breakwater or quays, the blocks are stacked up. FIG. 2 shows a portion of a breakwater constructed with such blocks, wherein each block substantially consists of three components, namely, a front wall portion 5 forming a perforated wall of the caisson, a rear wall portion 6 forming the rear wall of the caisson, and a uniting beam 7 integrally joining both front and rear portions 5 and 6.
A quay or breakwater with seams in a staggered pattern (FIG. 2) is constructed by disposing those blocks laterally on the same horizontal level and stacking up the blocks vertically while shifting the center lines of the blocks. A quay or breakwater constructed in the above manner can provide horizontal holes 8 which correspond to the horizontal holes 4 of the caisson.
The blocks need not necessarily be stacked up in a staggered zigzag pattern. For example, the blocks may be stacked aligning the sides of all blocks on the same vertical line. However, the stacking-up of blocks in a staggered pattern is most recommendable to achieve the uniform distribution of internal stress which may be caused in the structure during the block stacking operation and sufficient uniting of blocks which will be described later. As stated above, a breakwater or the quay constructed by stacking up the blocks provides energy dissipating functions equal to those of breakwaters constructed by a large-sized caisson. However, the block-made breakwaters still have a serious structural defect. Namely, there are no structurally firm connections among the blocks similar to toy building blocks. Accordingly, such breakwater may be destroyed easily be local internal stress induced by wave force, earthquake force, or unequal ground subsidence, even if the breakwater is constructed in a staggered pattern. Such cases have actually occurred. In order to prevent such disasters and provide stable and firm construction, it is essential to structurally firmly contact the blocks with each other.
Accordingly, it is an object of the present invention to provide blocks for constructing a breakwater or quay which can be structurally firmly connected to each other, thereby providing for constructing a breakwater or quay having sufficient rigidity, integration and strength.
In summary, the present invention discloses a block for constructing a breakwater, comprising (a) a front wall, (b) a rear wall disposed in parallel and spaced-apart relationship relative to the front wall, (c) and at least one partition wall disposed perpendicularly to the front and rear walls and integrally connecting the two walls to form at least one vertical open-ended chamber between the front and rear walls, wherein the improvement is characterized in that at least one vertical open-ended hole is formed on each of the front and rear walls of the block such that the vertical open-ended hole can be in alignment with corresponding vertical open-ended holes formed in the same manner on front and rear walls of the blocks in upper and lower rows when the blocks are arranged in rows and stacked vertically.